The following projects are planned to investigate the role of the electrochemical proton gradient across the mitochondrial inner membrane in oxidative phosphorylation: 1. measurements of the proton gradient in submitochondrial particles and comparison with the Gibbs free energy of ATP synthesis and of electron transfer in the respiratory chain, 2. overall efficiency of oxidative phosphorylation (P/O ratio) in mitochondria and submitochondrial particles, 3. stoichiometry of proton translocation in reconstituted cytochrome oxidase vesicles.